The design complexity of mobile radio frequency (RF) chips (e.g., mobile RF transceivers) is complicated by added circuit functions to support communications enhancements. Designing mobile RF transceivers may include using semiconductor on insulator technology. Semiconductor on insulator (SOI) technology replaces conventional semiconductor (e.g., silicon) substrates (e.g., wafers) with a layered semiconductor-insulator-semiconductor substrate for reducing parasitic device capacitance and improving performance.
SOI-based devices differ from conventional, silicon-built devices because a silicon junction is above an electrical isolator, typically a buried oxide (BOX) layer. A reduced thickness of the BOX layer, however, may not sufficiently reduce the parasitic capacitance caused by the proximity of an active device on the semiconductor layer and a semiconductor substrate supporting the BOX layer. The active devices on the SOI layer may include complementary metal oxide semiconductor (CMOS) transistors.
A high voltage power amplifier (e.g., core devices) and a high voltage switch (e.g., input/output (IO) devices) may be implemented using a type of CMOS transistor referred to as a laterally diffused metal oxide semiconductor (LDMOS) transistor. LDMOS transistors represent a type of an asymmetric power metal oxide semiconductor field effect transistor (MOSFET). LDMOS transistors are generally designed to achieve a low on-resistance and a high blocking voltage. These features may be supported by creating a diffused P-type channel region in a low-doped N-type drain region. LDMOS transistors fabricated on SOI substrates, however, suffer from reliability issues that prevent achieving the full performance potential offered by SOI technology.